Muslim

It has been narrated on the authority of Abu Musa that when the Messenger of Allah (ﷺ) deputed any of his Companions on a mission, he would say: Give tidings (to the people); do not create (in their minds) aversion (towards religion); show them leniency and do not be hard upon them.

It has also been narrated by Sa'd bin Abu Burda through his father through his grandfather that the Prophet (ﷺ) of Allah (ﷺ) sent him and Mu'adh (on a mission) to the Yemen, and said (by way of advising them): Show leniency (to the people); don't be hard upon them; give them glad tidings (of Divine favours in this world and the Hereafter); and do not create aversion. Work in collaboration and don't be divided.

It has also been narrated by Sa'd bin Abu Burda through his father through his grandfather that the Prophet (ﷺ) of Allah (ﷺ) sent him and Mu'adh (on a mission) to the Yemen, and said (by way of advising them): Show leniency (to the people); don't be hard upon them; give them glad tidings (of Divine favours in this world and the Hereafter); and do not create aversion. Work in collaboration and don't be divided.

Narrated to us by ‘Ubaydullah ibn Mu‘adh al-‘Anbari, narrated to us by my father, narrated to us by Shu‘bah, from Abu al-Tayyah, from Anas.
And narrated to us by Abu Bakr ibn Abi Shaybah, narrated to us by ‘Ubaydullah ibn Sa‘id.
And narrated to us by Muhammad ibn al-Walid, narrated to us by Muhammad ibn Ja‘far, both from Shu‘bah, from Abu al-Tayyah, who said: I heard Anas ibn Malik say: The Messenger of Allah, peace and blessings be upon him, said:
"Make things easy and do not make them difficult, and give tranquility and do not drive people away."